The traditional methods of making such orthotics involve the taking of a plaster cast of the patient's foot such as set out in U.S. Pat. No. 7,125,509 to the present inventor, which exemplify this art. Once the plaster cast has been made, a replica of the underside of the foot is fabricated and the final plaster orthotic is moulded onto that replica.
In particular, the abovementioned patent describes how the stance of the patient's foot can be corrected whilst the patient is bearing his or her own weight so as to correct inherent defects and thereby ensure that the cast is taken whilst the patient's foot is in the corrected position. This is because the foot alignment is physically manipulated from which position an orthotic for a corrected stance is advantageously provided.
It is also known to create an orthotic mould directly from the patient's foot with the moulding process being conducted whilst the patient is either lying down or sitting down. In either of these two positions no effort is made to correct the stance defects of the patient. Thus the practitioner is required to make an educated guess or apply some other method of determining how the orthotics should be further shaped so as to overcome any stance defects of the patient.
A recently developed method for producing a foot orthotic involves the use of either a pressure sensitive standing platform that typically takes the form of a deformable or pressure-sensitive mat having very many spaced sensors disposed in a two-dimensional array below the surface of or under the mat. With a patient standing on the mat, a map of the pressure exerted by the surface of the foot is provided. This image is then utilised to produce a three-dimensional model purporting to capture the shape of the foot and this image is then manipulated to attempt to account for a preferred shape or pressure map which would be corrective once the foot is bearing weight. This model can then be used to manufacture an orthotic by various means.
Whilst orthotics made by this method may provide some correction to a patient, they can only estimate the necessary corrective function. This is because the orthotic is formed from an image obtained by the patient standing on the mat without re-alignment to a corrected position. As such, the model is not obtained from a foot where force has actually been applied to realign it and place it into a more functional position and change the stresses placed on the foot due to misalignment. The use of 3-D laser scanning in place of pressure sensors has also become known. However, this method suffers the same defect as using pressure sensors. In each case, the apparatus required is relatively expensive.